Telephony.



E. R. CORWIN.

TELEPHONY.

APPLICATION FlLED APR. 7, 1912' 7 1,173,777. A Patented Feb. 29,1916.

5 SHEETSSHEET I.

INVJENTOR ELMER R C ORWIN ATTORNEY E. R. CORWIN.

TELEPHONY.

APPLlCATlON FILED APR. 7, 1915.

Patented Feb. 29,1916.

5 SHEETS-SHEET 2.

fi INVENTOR ELMERR. CORWIN.

ATTORNEY E. R. CORWIN.

TELEPHONY.

APPLlCATlON FILED APR.7,1915- Patented Feb. 29,1916.

5 SHEETSSHEET 3- INVENTOR ELMER R. CORWIN ATT ORNEY TELEPHONY.

APPLICATION FILED APR. 7, 1915.

Patented Feb. 29, 1916.

1,173,777. 5 SHEETSSHEET4 INVENTOR E LMER R. CORWIN ATTORNEY E. R. coawm.

TELEPHONY.

- APPLICATION FILED APR. 1, 19-15. 1,173,777. Patented Feb.29,1916.

5 SHEETSSHEET 5.

FIG.1 FIGZ FIGS FIGA 'FIG.5

34 d-TO OTHER CONTACTS 54 TO OTH ER CONTACTS A F 1G, 7 INVENTOR E LMER R. CORWIN ATTORNEY ELMER R. CORWIN, OF CHICAGO,

' OF CHICAGO, ILLINOIS,

ILLINOIS, ASSIGNOB 'IO FRANK B. COOK COMPANY,

A CORPORATION 01 ILLINOIS.

TELEPHONY.

Specification of Letters Patent.

Patented Feb. 29, 1916.

Application filed April 7, 1915. Serial No. 19,655.

To all whom it may concern: I

Be it known that I, ELMER R. Conwm, citizen of the United States, residin at Chicago, in the county of Cook and tate of Illinois, have invented a certain new and useful Improvement in Telephony, 'of which the following is a full, clear, concise, and exactdescription, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to telephone exchange systems and has for one of itsobjects the provision of improved equipment whereby calling lines or connected or are adapted for connection with calling lines may be brought into connection with further calling line extensions that pertain to difi'ering classes of service. By means of my invention said link connectors may, for example be interchangeably connected with special service lines such as extend to fire alarm and police stations; with other link connectors which enable calling and called lines to be connected at the same board; and with trunk lines whereby calling lines extending to one board may be connected with called lines extending to another board.

In practising my invention I employ motor devices for those of the aforesaid link connectors or line extensions which are nearest the calling lines and subdivide the range of operation of each motor device into portions that are respectively preferably individual or peculiar to the classes of further telephone line extensions to be added to the calling lines. In the preferred embodiment of the invention these motor devices employ one set of wipers which operate over waiting contacts that pertain to the further telephone line extensions, these wipers having their range of operation subdivided into portions that are respectively individual or peculiar to the classes of further telephone line extensions to be added to the calling lines, the line extensions of each class being represented in its portion of such range of operation by waiting contacts individual to the individual extensions so that the wipers, when operating in range, will be in selectable relation with the further line extension of another class or group, and so on. I desirably employ 'operator controlled means for determining the portion of the range of operation in which individually selectable by the operator.

link connectors that are one of said portions of its the motor device will be efiective for the purpose of taking part in adding the desired further extension to thecalling line.

According to one feature of the invention the extensions in a selected group are made According to anotherfeature of the invention the extensions in a selected group are made individually selectable independently of the operator, that is automatically and when freed from use. The motor device is desirably merely set into operation by the operator and automatically finds its association with the group of further extensions and a selectable extension in such group. As have practised the invention I include among the wipers of the motor device one wiper which operates over waiting contacts that are individual to the groups of further line extensions and which are included in circuits whose character is controlled by the receiving operator to determine the portion of the range of operation of the motor device in which the motor device will be effective. The wipers of the selector switches desirably work in fixed levels, in which case the range of travel of the wipers of each switch is subdivided into sections that are individual to the groups of line extensions. The invention, however, is not to be limited to the use of one level switches. I also in clude among the wipers of the motor device another wiper which operates over other waiting contacts that are individual to the various further telephone line extensions. The waiting contacts belonging to each group of further calling line extensions are themselves grouped and are tive association with the wiper which the motor device is operating in the portion of its range individual to such group of further line extensions There are other characteristics of my invention and the invention in its various features will be more fully explained by reference to the accompanying drawings showing one embodiment thereof and in which- Figures 1, 2, 3 and 4, taken collectively according to the arrangement illustrated in Fig. 5, show a telephone exchange system equipped in accordance with one embodiment of the invention; Fig. 6 is a simplified diagram illustrating some of the characteristics of the invention; and Fig. 7 diagrammatically illustrates a circuit detail.

limited to efiec- .-The telephone lines leading from the subscribers stations are shown as extending to manually controlled switches at an exchange, bein then desirably divided into groups thoug the nature of the exchange to which the lines extend and the relative disposition of the lines is immaterial so far as the invention is concerned.

The embodiment illustrated includes spring jacks 6 at the first board of the exchange, each line having a plurality of these spring jacks in multiple relation which are apportioned among the diflerent divisions of the first or main board whereby all lines extending to this board may be'connected for conversation. When a subscriber at station 200 or 250 initiates a call by removing his receiver from its switch hook circuit is 1 established through his line lamp 7 which is preferably of fifteen hundred ohms resistance, which circuit is traceable from the common grounded battery 8 (desirably of fifty volts and whose illustration is repeated for the sake of clearness), through the line lamp, the armature switch and normal contact of the cutoff relay 9 (preferably of two hundred fifty ohms resistance) the switch hook 1 at'the calling station, the telephone receiver and transmitter bridge at this station, to the grounded cutofl" relay. Owing to the resistance of the lamp and relay there is not present, at this time, sufficient current to energize the relay. The operator to whom the lamp and answering jack 6 to which it is individual are assigned will insert the answering plug 10 within the jack of the calling line, the first consequence of this act being the energization of the cutofl relay 9 and the consequent exclusion of the lamp 7 from circuit owing to the establishment of a circuit traceable from the grounded battery 8, the left hand armature switch of the calling subscribers supervisory relay 11 and its follow up contact, the calling subscribers supervisory signal 12 (which does not have opportunity to glow at this time), the tip of the answering plug, the tip spring of the answering jack, to the grounded winding of the cutoif relay, this relay being then energized as the lamp 12 is of sufiiciently low resistance. Circuit for relay 11 is now established'traceable from the grounded battery 8, through the winding of the relay 11, the sleeve of the answering plug 10, the sleeve spring of the employed answering jack, the alternate contact of the armature switch of cutoff relay 9 and said I armature switch, both sides of the calling line, to the grounded winding of the relay 9 whereby the circuit for this latter relay is maintained after the initial circuit therefor is broken at the left hand armature switch of relay 11. The circuit which includes the relays 9 and 11 also is the circuit by which battery current is supplied to the calling subscribers transmitter. The operator uses her telephone equipment 13 to converse with the calling subscriber to ascertain his wants, this equipment being shown as including terminals 14 in the form of wipers of a master switch which is common to the link connectors that have the answering plugs 10 at her position. These wipers 14 and other wipers 'of the master switch are caused normally to rest in association with'some idle answering plug and when so associated the signal lamp 15 individual to such answering plug (there being one signal lamp for each answering plug at each operators position) is caused to glow so that the operator will employ the plug 10 to which the glowing lamp is individual in answering the calling subscriber, the operator being thrown into telephonic connection with the calling subscriber immediately upon the insertion of the answering plug (or when the answering link is in any other manner coupled with the calling line) by a circuit which is apparent and without manipulating any key. These characteristies are broadly covered in a co-pending apgrounded battery 8, through the wiper 17 of the master switch, the waiting contact engaged by this wiper, the lower winding of the relay 16, the armature switch immediately above the core of relay 18 and its con tact, the" wiper 19 at the called line end of the employed answering link having the answering plug 10, the waiting contact engaged by this wiper, the intermediate armature switch of relay 20 and its normal contact, the left hand intermediate armature switch of relay 21 and its normal contact, to ground, the relays 20 and 21 being common to the answering links having the answering plugs 10 at the operators position while the waiting contacts for the wipers of the master switch are divided into sets each individual to an answering link. All of the switches having the wipers 19 at an operators position have multipled waiting contact engageable by this wiper whereby the wiper 19 of any switch having it at an operators position may have access to the grounded left hand intermediate armature switch of relay the circuit traced, such circuit being dependent upon the association of the master switch with the answering link having the employed wiper 19; The circuit traced through the lower winding of the relay 16 energizes this relay to close the clearly apparent circuit for the lamp 15 belonging to the answering link with which the aforesaid master switch happens to .be in association, this circuit being maintained to cause the lamp 15 to glow so that the operator is antomatically instructed to employ the answering link to which this glowing lamp is individual inasmuch as this is now the only link by which she may hold telephonic communication with the calling subscriber.

The armature switches of the relay 16 remain attracted during the time that the answering link (designated by this signal 15 and with which the master switch is associated) is idle and until a further calling line extension added thereto is further extended, whereby there may be no faulty operation of the relay 18 prior to the addition of a further calling line extension and the time such extension itself is further extended. There is one relay 18 individual to each answering link serving when energized to cause the master switch to move out of association with its link and when deenergized permitting the master switch to come into association with its link, the master switch having its wipers moving in uniform direction that come to rest in association with the waiting contact, first encountered, that are individual to an answering link having a deenrgized relay 18. The motor device having the wiper 19 also includes a wiper 22 whose waiting contacts are included in controlling circuits that are individual to further calling line extensions that include connecting plugs 23 at the same positions having the operators telephone outfits 13. These connecting plugs have grounded plug seat switches 24 provided with norinal and alternate contacts engaged thereby respectively when the plugs are in and out of their seats. When the wiper 22 at the called line end of an answering link engages a waiting contact that is grounded at a plug 23 individual. to this waiting contact circuit through the upper winding of relay 16 is maintained over a path traceable from the grounded plug seat switch 24 of such plug 23, the normal contact of this switch, the wiper 22 and the waiting contact individual to the plug 23 and its switch, the intermediate or middle armature switch of relay 18 and its normal contact, the upper winding of relay 16, the wiper 25 of the master switch, and the waiting contact engaged thereby the battery 8, to ground. When the plug 23 is taken for use and when the assoswitch of relay 16 and its normal contact, the

right hand armature switch of the now energized calling subscribers supervisory relay [1, its contact; to ground. The energized relay 18 now establishes a circuit to occasion the operation of the motor magnet 26 and which circuit is traceable from the grounded bottom armature switch of relay 18, the contact of this switch, the wiper 27 of the master switch and the waiting contact engaged thereby and individual to the relay 18, the relay 28', the battery 8, to ground. The relay 28 in turn establishes a circuit traceable from the grounded battery 8, through the winding of the motor magnet 26, the driving armature and contact of this motor magnet, the armature switch of relay 28 and its contact, to ground. The motor magnet 26 is now operated until the wiper 27 engages a waiting contact which is individual to deenergized relay 18 to which this relay is in turn individual. The operation of the master switch that will bring it into association with a new answering link that is next to be. employed does not occur until the motor (leyice having wipers 19 and 22 at the called line end of the answering link designated for use by the signal 15 is included in connection with a further calling line extension that has been associated with the wanted line, such association being followed by the energization of the relay 18. When the operator has ascertained the line wanted she will operate the switch or button 29, 30 or 31 which is individual to the board at which the wanted line terminates, lines to be called for being represented directly or indirectly by waiting contacts in the line extending switch having the wipers 19, The talking waiting contacts which are individual to the various further calling line extensions are traveled over by the Wipers 32 and 33. The waiting contacts pertaining to the wipers 22, 32 and 33 may be apportioned or assigned for use in effecting connection with lines (to which they pertain and which they represent) that terminate at different boards and also with lines that terminate at the main board and may also be employed in association with speclal service lines to take 200, 250 extend and which button is used in v connection with plugs 23 in establishing local connections. The button 29 is individual to the group of special service lines 34 extending to' a special operators position. The special operators may be employed for any special purpose. For example the equipment of special operators may be locatedat fire alarm stations or may belong to supervisory operators or chief operators.

The button 30 is shown as being individual to a second board which may be provided with lines similar to the first board with which calling subscribers at the first board may have connection and vice'versa and from which second board other trunk lines may extend to the first board.

Fig. 6 somewhat more generally indicates the interrelation of the switch having the wiper 19 with the calling line extensions that are to be added to the answering links, the waiting contacts being arranged in sets, the contacts of each set being simultaneously engageable by the wipers 19, 22, 32 and 33. In Fig. 6 each set of these wipers is indicated by a single wiper 32 and each set of waiting contacts is indicated by a single contact 32 for the sake of clearness. The connecting plugs 23 or other connecting switches, the special lines 34 and the trunks A leading to the second board are provided in sufficient number to take care of the peak load conditions which may arise in any of the three classes of service. There are as many switches having wipers 32 as there are answering links having answering plugs 10 (each such switch being individual to a plug 10), the motor switches under the operators control at each position having a master switch common thereto as has been described, each of the first aforesaid motor switches at an operators position having, access to all of the calling line extensions that may be added to the answering links because of the multipled connection of the waiting contacts individual to said calling line extensions that are included in the switches having the Wipers 32* at a position. For example, if there are ten connecting plugs 23, two special service lines 34, and ten trunks A going to the second board, each switch having wipers 32 may have access to twentytwo calling line extensions because of the multipled relation of the waiting contact terminals of these calling line extensions. The plugs 23 and the calling line extensions to which they are individual are divided into groups, each group being individual to and restricted to an operators position so that the switches at each operators position having wipers 32 do not have access to the connecting plugs at other operators positions. The waiting contact terminals of the special lines 34 and the trunks extending to the second board (but not those waiting contacts pertaining to the extensions having the plugs 23, which latter conpositions.

tacts are only multipled at each operators position) are, multipled throughout the switches of a plurality of operators.

The buttons 29, 30 and 31 overn'or modify the character ofthe circults having the waitingcontaets over which the wipers 19 move. Those waiting contacts 23 in each switch over which a wiper 19 moves and which are individual to the connecting plugs 23 are directly connected in each such switch to constitute an electrical unit, similar units being multipled throughout the motor devices at each operators position, an alternative construction being to merge these particular waiting contacts into a single segmental contact plate, which alternative construction is not desired because of manufacturing reasons. These waiting contacts 34* of each switch over which the wiper 19 moves and which are individual to the special lines 34 are also directly connected in such switch to constitute an electrical unit, these electrical units being multipled throughout the motor devices at a plurality of operators positions. Likewise those waiting contacts A of each switch over which the wiper 19 moves and which are individual to the trunks A extending between the first and second boards are directly connected in such switch to constitute an electrical unit which also are multipled throughout the motor devices of a plurality of operators Thus there are, in efiect, but three waiting contacts over which the wiper 19 of each switch having this wiper passes, one such contact being individual to the group of connecting plugs 23 at an operators position, another such contact being individual to the collection of special lines 34 and the third of such contacts being individual to the collection of trunk lines A extending between the boards. If the connection to be established is a local connection the operator will insert some idle plug 23 in the jack 6 of the wanted line, immediately after she learns the number ofthe wanted line, the link individual to this plug being thereby made selectable, ground being removed at the plug seat switch of the employed plug, from that waiting contact individual to this plug 23 and which pertains to wiper 22 to enable this wiper and the switch including it to stop when this waiting contact is reached. The operator then depresses the button 31 to alter the electrical character of the group of directly connected contacts over which the wiper 19 passes and which group of waiting contacts belongs to the group of links having the employed plug 23.

In the embodiment of the invention illustrated a depression of the button or key 31 is accompanied bv the establishment of a circuit which is traceable from the grounded battery 8, through the winding of relay 20, the contacts of-the button 31, to ground.

' To enable the button 31 to be released the relay 20 establishes a locking circuit through itself which includes the left hand armature switch of this relay and the contact engaged thereby, the alternate contact of the intermediate armature switch of relay 16, the right hand armature switch of relay 1-1 and the grounded contact thereof. The intermediate armature switch of relay 20 establishes a circuit traceable from the grounded common battery 8, through the winding of the motor magnet 36, the armature and contact, of this motor magnet, the lowermost armature switch of relay 16 and its contact, the alternate contact of the in termediate armature switch of relay 20, the normal contact of the left hand intermediate armature switch of relay 21, this armature switch, to ground. The motor magnet 36 operates to effect relative movement between its wipers 19, 22, 32 and 33 and the contacts for these wipers. The motor magnet 36 will be continued in operation (assuming that the wipers 19 etc. do not already happen to be associated with the plug 23 taken for use) until the wiper 19 encounters the group of directly connected waiting contacts that is individual to the group of plugs containing the employed plug 23 (assuming that the connection is locally established) and from which ground has been removed at the intermediate armature switch of relay 20, this motion immediately stopping if the first waiting contact then encountered by the wiper 22 is individual to the plug 23 that has been taken for use or continuing until the wiper 22 finds such waiting contact. The wipers 19 and 22 enter upon each waiting contact before leaving the preceding waiting contact in order that the switch may turn under the circumstances related while the talking wipers 32 and 33 leave waiting contacts before entering upon other contacts in order to avoid disturbing clicks. Ground now' being removed from the wipers 19 and 22, the windings of relay 16 are denergized. Circuit for the driving magnet 36 is -thereupon open at the bottom armature switch of relay 16 to permit the wipers pertaining to this driving magnet to remain at rest. Circuit is established through the relay 18 at the intermediate armature switch of relay 16, which circuit is traceable from the grounded battery 8, through the winding of relay 18, the intermediate armature switch of relay 16 and its normal contact, the right hand armature switch of relay 11 and its contact, to ground. The relay 18 establishes a circuit traceable from its grounded armature switch, through its then engaged contact, the wiper 27 of the master switch, the waiting contact individual to the relay 18 and its associate answering link, the relay 28, the grounded battery 8, to

' is individual. The two uppermost armature ground. The relay 28 establishes a circuit traceable from its grounded armature switch and contact, the armature and contact of the motor magnet 26, the winding of said motor magnet, the. battery 8, to ground. The motor magnet thereupon steps the wipers 14 etc. around until the wiper 27 encounters a waiting contact which is individual to the next deenergized relay 18 whereupon circuit for the motor magnet is. opened at the bottom armature switch of such relay 18 to permit the wipers of the master switch to remain in association with the unemployed link to which this new relay 18 switches of the energized relay 18 belonging to the answering link taken for use complete the talking sides of the link intervening between the employed plug 10 and the employed wipers 32, 33. The intermediate or middle armature switch of the energized relay- 18 establishes a gap in the circuit of-the upper winding of relay 16 so that this winding cannot again be energized and engages its alternate and grounded contact to place ground upon the wiper 22 so that no other switches will stop at waiting contacts multipled with the waiting contact engaged by said wiper. The denergized relay 16 of the answering link taken for use causes the relay; 20 to be denergized by breaking the circuitfor this relay 20 at the intermediate armature switch of relay 16. Ground is placed upon the group of directly connected waiting contacts which are connected with 1 the wiper 19 and which group is individual to the group containing the employed plug 23, this ground being traceable from the left hand intermediate armature switch of relay 21 and its normal contact, the interice mediate armature switch of relay 20 and its normal contact, to said group of contacts and the other similarly positioned groups of waiting contacts in multiple therewith, whereby the relay 16 of the link with which 116 the master switch newly comes into association will become energized to light the lamp 15 to designate this new link as the one next to'be used, assuming that the wiper 19 of the new link is in connection with a 115 group of contacts in multiple with the group engaged by the switch having the wiper 19 that has been employed in extending the calling line locally.

After the employed plug 23 is removed .123 from its plug seat switch 24 for entry within the jack 6 of the wanted line, a circuit is established by way of the alternate contact of the plug seat switch which is traceable from ground, said plug seat switch, the 125 alternate contact of the switch, the right hand armature switch of relay 37 and its normal contact, the winding of relay 38, the battery 8, to ground. The relay 38 is thereupon energized to attract its armature 133 switches. If the wanted line is busy the lower intermediate armature switch of relay 38 establishes a circuit traceable from ground, this armature switch, the contact thereof, the lower winding of testing relay 39, the top armature switch of relay 40 and its normal contact, the tip of the employed plug 23, the tip spring of the jack 6 multiplied with the foregoing jack (in the event that the wanted busyline is a previously called line), the tip of another plug 23 engaging the tip spring of this second jack, the upper armature switch of the relay 40 individual to this latter plug and its alternate. contact, the associate impedance 41, the battery 8, to ground. Another test path may be traced which is present if the busy wanted line is a calling line and which path exists before such calling line is connected with 1 its called line. A portion of this path is similar to the path portion initially traced up to the tip contact spring. of the jack of the wanted line, from which point the path continues over both sides of the wanted (previously calling) line, the armature switch 'of cutoff relay 9 of the wanted (previously calling) line, the alternate contact of this armature switch, the sleeve spring of the answering jack of the wanted line, the

sleeve of the answering plug 10 engaging the answering jack, the winding ofsupervisory relay 11, the battery 8, to ground. The calling party is apprised of the busy condition .of the wanted busy line by the busy signal which initiates in the primaryintermittently established test current producing circuit 42 which is in inducing relation with the secondary 43 that is included in bridge of the tip and sleeve. sides of the link having the plug 23, which bridge is traceable from the contact of the top armature switch of relay 39, said armature switch,

the condenser 43*, the secondary 43, the bottom armature switch of relay 39, to the contact of this armature switch, said armature switch contacts being respectively connected with portions of the tip and sleeve strands. This bridge connection is brought into circuit relation with the calling line when the button 31 is depressed to move the armature switches of relay 18 associated with the calling line and after the wipers'32 and 33 have become connected with the link having the employed plug 23. The calling subscriber will usually place his telephone upon its switch hook when he receives the busy test manifestation relayed to him from the circuit 42 by way of the secondary 43. When the calling line has been extended to the link having the employed plug 23, a circuit is established from ground through the common battery 8, relay 44, wiper33 and the 'waiting contact engaged thereby, the next to the topmost armature switch of the relay 18 and its engaged contact, the impedance coil 45 bridged across the answering link upon the called line side thereof (which side is separated from the calling line side of the answering link by condensers 46) the top armature switch of relay l8 and its engaged contact, the wiper 32 and the waiting contact engaged thereby, the left hand winding of relay 37 to ground. The relay 44 is energized to establish a circuit traceable from ground, the upper armature switch of relay 44, the contact engaged by this armature switch, the top armature switch of relay 38 and the contact engaged thereby, the intermediate armature switch of relay 39 and its alternate contact, the upper winding of this relay, the battery 8, to ground. The circuit thus established is local to the exchange and operates to maintain the relay 39 energized during the time that the calling subscribers supervisory relay 11 is energized to maintain the relay 18 energized, that is during the time the calling subscriber has his receiver off its switch hook. Thus the calling subscriber is placed in control of the busy back-test relay 39. The lower armature switch of relay 44 also establishes a circuit traceable from ground, this armature switch, the contact thereof, the lower armature switch of relay 45 and its contact, the upper intermediate armature switch of relay 38 and its contact, the winding of relay 38 (which relay is slow to release), the battery 8, to ground whereby the relay 38 is maintained energized after the relay 37 is energized, the relays 37 and 44 being substantially simultaneously energized. The energized relay. 37 establishes a locking circuit for itself traceable from ground, the common battery 8, the right hand winding of this relay, the alternate contact of the right hand armature switch thereof, said armature switch, the alternate contact of plug seat switch 24, said plug seat switch, to ground.

The left hand armature switch of relay 37 applies ground to the waiting contact engaged by the Wiper 22 and all other waiting contacts at the same operators position in multiple therewith whereby no other switches having wipers 22- at such operators position can enter into connection with the link having. the employed plug 23, a

protection which endures until the plug 23 is winding of relay 40, the battery 8, to ground. The relay 40 is now energized, the top armature switch thereof engaging its alternate J to the normal contact of the ringmg relay 46 The intermediate armature switch of relay 40 establishes a circuit for the ringing relay 46 which is traceable from ground, the battery 8, the winding of ringing relay, the intermediate armature switch of relay 40, the contact of this armature switch, the bottom armature switch of relay 38 and its contact, the interrupter 47, to ground. The interrupter 47 causes the ringing relay 46 to be intermittently energized to effect the intermittent inclusion of the ringing generator 48 in circuit with the called line to operate the signal bell 4 thereat. The ringing current finds passage over both sides of the called line and the signal bell at this substation by way of the lower armature switch of relay 46 and its alternate contact, the sleeve of the employed plug 23, the sleeve spring of the employed jack, the tip of the employed jack, the tip of the employed plug 23, the upper armature switch of relay 46*, the contact engaged by this armature switch, theresistance 49, the battery 8, to ground. It is understood that the cutoff relay 9 of an unemployed called line is energized when the plug 23 is connected therewith in order that ringing current may find its passage to the called station, the circuit for this cutofi relay being traceable from ing of said cutofi relay, the tip spring of the employed jack 6, of the called line, the tip of the plug 23 engaging this spring, the top armature switch of relay 40 and its alternate contact, the impedance 41, the battery 8, to ground. After the called subscriber responds and'during a period of deenergization of the ringing relay 46 a circuit is established which is traceable from ground, through thebattery 8, the winding of called subscribers supervisory relay 45*, the bottom. armature swltch of relay 40 and its contact, the bottom armature switch of relay 46 and its normal contact, the sleeve of the employed plug 23, the sleeve of the jack 6 of the called line, both sides of the called line and the telephone bridge at this substation, the winding of the cutoff relay 9 of the called line, to ground. The holdlng circuit for relay 38 is now broken at the lower armature switch of relay '45 but as the relay 38 is slow to release its armature switches are maintained in attracted positions suflicientlylong to enable the establishment of a circuit traceable from ground,

the upper armature switch of relay 45, the contact of this swltch, the intermediate armature switch of relay 39 and its normal conground, the windtact, the winding of relay 40, the battery8, to ground, the establishment of this circuit occurring during the time that the top armature switch of the relay 38 takes part in maintaining the previously established C11- cuit through relay 40 by way of the upper armature switch of relay 44. Thus the relay 40 is maintained energized during the perlod of the transfer of its control from the calling to the called subscriber. By making the relay 38 slow to release connections between calling and called subscribers will not be automatically broken down consequent upon accidental quick movements of the swltch hooks.

If a special line 34 is to be put into connection with the calling line the button 29 is depressed to 'unground the directly connected group of contacts 34 pertaining to the lines 34 and over which the wiper 19 of the employed switch may travel to enable the wiper 19 to reach this group of contacts to place the wiper 22 into connection with a waiting contact individual to an idle one of the lines 34, the wiper 22 stopping in connection with the first of such of its contacts which it reaches. \Vhen a line 34 is thus taken for use it is made busy to guard against its selection by another switch at any operators position due to the establishment of ground. upon the wiper 22 at the intermediate armature switch of relay 18, which relay is energized after the depression of the button 29 and when the wiper 22 is brought to rest into connection with a previously idle line 34. When a line 34 has become selected the bridge at 45 serves to establish a circuit through the relay 50 which is traceable from ground, the upper winding of relay 50, the tip side of the seleeted line 34, the wiper 32 and the waiting contact engaged thereby and which contact is individual to the selected line 34, the top armature switch of relay 18, and its contact, the bridge 45, the next to the top armature switch of relay 18 and its contact, the wiper 33, the waiting contact engaged by this wiper which is also individual to the employed line 34, the bottom winding of relay 50, the battery 8,,to ground. The relay '50 thereupon attracts its armature switches, the two upper armature switches including the special operators telephone 35 in circuit with the calling line after the telephone key 50 has been depressed, while the bottom armature switch of relay 50 closes the circuit of the signal device 51 to attract the attention of the operator having the equipment 35. The button 29 enables the selection of an idle line 34 in a manner similar to that in which a similar function was performed by the button 31. In the present instance the depressed button 29 operates to establish a circuit traceable from ground,

7 the springs of the button, the contact engaged by one of these springs, the relay 21, the battery 8, to ground. The right hand intermediate armature switch of relay 21 places ground upon the group of connected waiting contacts 23 individual to the plugs 23 at the operators position having the key 29 so that the wiper 19 will pass over such group of directly connected contacts 23 (if these contacts 23 happen to be between the wiper 19 and the contacts 34 in seeking the group of ungrounded contacts 34 that is invidual to the group of lines 34. The right hand armature switch of relay 20 normally places ground upon the directly connected waiting contacts A that are individual to the group of trunk lines extending between the first and second boards whereby the wiper 19 will pass over these connected contacts in seeking the group containing the wanted extension 34 having the contactsA are between the wiper 19 and the contacts 34. When any group of-directly connected waiting contacts over which the wiper 19 moves is ungrounded for the purpose of selecting a group of calling line extensions individual thereto, the two remaining groups and directly connected waiting contacts over which the wiper 19 travels are grounded so that the range of effective operation is confined to the movement of the wiper 22 over the waiting contacts individual to the calling line extensions of the selected group. If the group of calling line extensions in the form of trunks extending between the first and second boards is to be selected, the

button 30 is depressed to unground the group of directly connected contacts A individual thereto and over which the wiper 19 passes to bring the wiper 22 to that portion of its range of movement in which waiting contacts individual to these trunks are included. Ground from such group of directly connected contacts is removed at the extreme right hand switches of the relays 20 and 21, which relays are now both energized due to obvious circuits established through these relays at the contact springs of the button 30. The wiper 22 and its associates are automatically placed in connection with an idle trunk line extending between the boards in a manner similar to that in which these wipers may be connected with an idle line extension in the group having the plugs 23 or the lines 34, as hitherto described, and the established connection is guarded in a manner similar to that described in connection with a selected line 34. The lines 34 and the trunks A are made selectable by line equipment of the calling lines when the telephone receivers at the sub stations are restored to their switch hooks,

It may be said that when relay 21 is energized it has a locking circuit established for it similar to that which is established for the relay 20. It is also to be noted that the association of the master switch having the wipers 25 etc. is governed in the manner hitherto described irrespective of the line extensions 23, 34 or the trunks which are connected with the answering line. It is also apparent that the driving magnet 36 is operated when either realy 20 or 21 is energized for the purpose of driving the wiper 19 to that portion of the range of operation ,in which the wiper 22 is to become effective having the wiper 19 has its range of'movement divided into three parts though the invention is not to be limited to the division of the range of operation into distinct portions), one part individual to the group of line extensions having the connecting plugs 23, a second part individual to the group of line extensions 34, and the third part indi-- vidual to the group of trunk lines A extending between the first and second boards. In the first part of the range of, operation are placed the waiting contacts pertaining to the line extensions having the plugs 23 and in which range portion are included the contacts 23*. In the second part of the range of operation are placed the waiting contacts pertaining to the line extensions 34 and in which range portion are included the contacts 34?. In the third part of the range of operation are placed the waiting contacts pertaining to the trunks A extending between the first and second boards and in which range portion are included the con- The keys 31, 29 and 30 are respectively'individual to these three portions of said range of operation and serve to select the portion of the range of operation in which the wiper 22 is to become efiective to pick out the line extension in the group line is to be extended.

The second board is arranged similar to the first board and similar parts having similar functions are given similar characters of reference with the exception that the subdetermines the route over which the calling l 25 portions of the trunk line equipments similar to corresponding parts at the exchange ends of subscribers? lines being given similar characters of reference with prime exponents added.

I employ answering links which terminate at their called line en'dsin the switches having wipers 19, 22, 32 and 33 in order to increase the capacity of the exchange but I do not wish to be limited to the employment of these answering links for effecting the association of such with calling lines.

In passing, attention is invited to the location of the plugs 10 and 23 at the same operatorsposition and the provision of the selector switches having the wipers 19 for coupling the calling line link connector sections (to the left of these switches) interchangeably with the right of these switches). Some claims are drawn to these characteristics.

While I have herein shown and particularly described the preferred embodiment ofmy invention I do not wish to be limited to'the precise details of construction and circuit arrangement shown as changes may readily be made without departing from the spirit of my invention, but

Having thus described my invention I claim as new and desire to secure by Letters Patent the following 1. A telephone exchange system including telephone lines; three groups of extensions for such telephone lines; two electro-mag-- nets and means associated therewith for selectively and interchangeably associating said groups of line extensions with telephone lines. one magnet serving to effect such association of one group of line extensions, another electro-magnet serving to efi'ect such association of another group of line extensions and the two electro-magnets together serving to eifect such association of the remaining group of line extensions; three operator controlled switches respectively individual to the difierent groups of line extensions; and circuit connections whereby one switch controls one magnet, another switch the other magnet and the third switch both magnets. 1

2. A telephone exchange system including telephone lines; three groups of extensions for such telephone lines; an electro-magnetic switch, having a motor magnet, for selectively and interchangeably associating said groups of line extensions with telephone lines; a relay for governing said motor magnet; two electro-magnets and means associated therewith for determining the exthe called line sections (to sections a master switch tent of operation of the motor magnet to associate the difierent groups of line extensions with the line and, after a desired selection, cooperating with the aforesaid relay then to stop the motor magnet; three operator controlled switches respectively individual to I the different groups of hue extenslons; and circuit connections whereby one switch controls one magnet, another switch the other magnet and the third switchboth magnets.

3. A telephone exchange system including telephone lines extending to an operators position at an exchange; link connectors at this position for unitinglines in conversation; means whereby the calling line and called line sections of these link connectors may be interchangeably associated; and a master switch interchangeably associated with the calling line sections for predetermining the calling line sections for use and governed by the called line sections when operatively coupled with. calling line sections.

4. A telephone exchange system including telephone lines extending to an operators position at an exchange; link connectors at this position for uniting lines in conversation; selector switches whereby calling line and called line sections of these link connectors may be interchangeably associated; and a master switch interchangeably associated with the calling line sections for predetermining the calling line ends for use and governed by the called line sections when operatively coupled with calling line sections.

5'. A telephone exchange system including telephone lines extending to an exchange; link connectors at the exchange for uniting lines in conversation; selector switches whereby calling line and called line sections of these link connectors maybe interchangeably associated; and a master switch interchangeably associated with the calling line for predetermining the calling line ends for use and governed by the called line sections when operatively coupled with calling line sections.

6. A telephone exchange system including telephone lines extending to an operators position at an exchange; link connectors at this'position for uniting lines in conversation; selector switches wherebv calling line and called line sections of these link connectors may be interchangeably associated; interchangeably I associated with the calling line sections for predetermining the calling line ends for use and governed by the called line sections when operatively coupled with calling line sections; and means whereby the called line sections are rendered individually selectable when taken for use.

7. A telephone exchange system including telephone lines extending to an exchange; link connectors at the exchange for uniting lines in conversation; .selector switches whereby calling line and called line sections 5 of these link connectors may be interchangeably associated; a master switch interchangeably associated with the calling line sections for predetermini-ng the calling line ends for use and governed by the called line I0 sections when operatively coupled with calling line sections; and means whereby the called line sections are rendered individi ally selectable when taken for us In Witness whereof, I hereunto subscribe my name this 5th day of April A. D., 1915. 1

ELMER R. CORWIN.

Witnesses;

G. L. CRAGG, E. L. WHITE. 

